Large pivot sprinkler devices are commonly used to irrigate large fields of row crops. The pivot sprinkler comprises an elongated tubular member which is supported at various points along its length by means of a wheeled upright support or tower. Water enters the tubular member at one end (e.g., at the center of the field) and exits the tubular member through sprinkler heads at various points along its length to irrigate the crops under the sprinkler. Each wheeled upright support includes two driven wheels to thereby cause the sprinkler unit to rotate about its fixed end (where the water is pumped into the tubular member). Consequently, the sprinkler unit pivots in a large circle. Thus, this type of sprinkler system is often referred to as a center pivot sprinkler system.
Occasionally a wheel on one of the support members or towers requires repair or replacement. Similarly, there is an occasional need to repair or replace a gear box on one of the support members.
For example, a tube in a tire may fail, or a valve stem may break, or a hub may break, etc. As a result, the wheel would have to be replaced or repaired. This means that the tower would have to be jacked up, the wheel removed and transported out of the field to a repair shop, and a replacement wheel would have to be transported into the field and to the tower. Also, if a gear box failed and required repair at a repair shop, the gear box must be taken off and transported out of the field, and a repaired or new gear box would have to be transported into the field and to the tower.
These items are bulky and very heavy. For example, a wheel could weigh about 400 pounds if it is caked and filled with mud.
Consequently, it is not practical to attempt to manually transport or carry a wheel or even a gear box to or from a tower in the field. This is especially true if the tower requiring the repairs is located near the center of the field. The task is made even more difficult when you consider that the soil has been irrigated and therefore is quite soft and muddy. Also, the humidity in the field is very high.
Although one could use a tractor and trailer, or a pickup truck, to transport repair items to and from the tower requiring repair, this results in at least two rows of crops being knocked down or ruined. Typical spacing of row crops in fields is about 30 inches. Naturally, a tractor or a pickup truck is several feet wide and therefore requires considerable space as it moves through a field. Also, more crops must be trampled if the tractor or truck is to be turned around when it reaches the tower requiring the repairs.
It is possible to hang a replacement wheel on a tower in anticipation of a wheel needing replacement. However, this adds extra weight to the sprinkler system and also involves much expense in larger systems where there may be, for example, twenty wheels present.
There has not heretofore been provided effective or efficient apparatus or techniques for transporting repair items to and from a tower or support structure in a center pivot sprinkler irrigation system.